Induced magnetic fields in aromatic [n]-annulenes-interpretation of NICS tensor components

The components of nucleus-independent chem. shift (NICS) tensors for Dnh n-annulenes are discussed as indexes of the arom. character of electronic pi systems. The component corresponding to the principal axis perpendicular to the ring plane, NICSzz, is found to be a good measure for the characterization of the pi system of the ring. Isotropic NICS values at ring centers contain large influences from the sigma system and from all three principal components of the NICS tensor. At large distances away from the ring center, NICSzz, which is dominated by contributions from the pi system, characterizes NICS well. [on SciFinder (R)]